"""重构：模块game_functions"""
import sys
from time import sleep

import pygame

from bullet import Bullet
from alien import Alien


def check_keydown_events(event, ai_settings, screen, ship, bullets):
  # 响应按键
  if event.key == pygame.K_RIGHT:
    ship.moving_right = True
  elif event.key == pygame.K_LEFT:
    ship.moving_left = True
  elif event.key == pygame.K_SPACE:
    fire_bullet(ai_settings, screen, ship, bullets)
  elif event.key == pygame.K_q:
    sys.exit()


def check_keyup_events(event, ship):
  # 响应松开
  if event.key == pygame.K_RIGHT:
    ship.moving_right = False
  elif event.key == pygame.K_LEFT:
    ship.moving_left = False


def check_events(ai_settings, screen, stats, sb, play_button, ship, aliens,
                 bullets):
  # 响应键盘和鼠标事件
  for event in pygame.event.get():
    if event.type == pygame.QUIT:
      sys.exit()
    elif event.type == pygame.KEYDOWN:
      check_keydown_events(event, ai_settings, screen, ship, bullets)
    elif event.type == pygame.KEYUP:
      check_keyup_events(event, ship)
    elif event.type == pygame.MOUSEBUTTONDOWN:
      mouse_x, mouse_y = pygame.mouse.get_pos()
      check_play_button(ai_settings, screen, stats, sb, play_button,
                        ship, aliens, bullets, mouse_x, mouse_y)


def check_play_button(ai_settings, screen, stats, sb, play_button, ship,
                      aliens, bullets, mouse_x, mouse_y):
  """Start a new game when the player clicks Play."""
  button_clicked = play_button.rect.collidepoint(mouse_x, mouse_y)
  if button_clicked and not stats.game_active:
    # Reset the game settings.
    ai_settings.initialize_dynamic_settings()

    # Hide the mouse cursor.
    pygame.mouse.set_visible(False)

    # Reset the game statistics.
    stats.reset_stats()
    stats.game_active = True

    # Reset the scoreboard images.
    sb.prep_score()
    sb.prep_high_score()
    sb.prep_level()
    sb.prep_ships()

    # Empty the list of aliens and bullets.
    aliens.empty()
    bullets.empty()

    # Create a new fleet and center the ship.
    create_fleet(ai_settings, screen, ship, aliens)
    ship.center_ship()


def fire_bullet(ai_settings, screen, ship, bullets):
  # 如果还没有到达限制，就发射一颗子弹
  # 创建一颗子弹，并将其加入到编组bullets中
  if len(bullets) < ai_settings.bullets_allowed:
    new_bullet = Bullet(ai_settings, screen, ship)
    bullets.add(new_bullet)


def update_screen(ai_settings, screen, stats, sb, ship, aliens, bullets,
                  play_button):
  # 更新屏幕上的图像，并且换到新屏幕
  # 每次循环时都重绘屏幕
  # 设置背景颜色
  screen.fill(ai_settings.bg_color)

  # 在飞船和外星人后面重绘所有子弹
  for bullet in bullets.sprites():
    bullet.draw_bullet()
  ship.blitme()
  aliens.draw(screen)

  # Draw the score information.
  sb.show_score()

  # Draw the play button if the game is inactive.
  if not stats.game_active:
    play_button.draw_button()

  # 让最近绘制的屏幕可见
  pygame.display.flip()


def update_bullets(ai_settings, screen, stats, sb, ship, aliens, bullets):
  # 更新子弹的位置，并删除已消失的子弹
  # 更新子弹的位置
  bullets.update()

  # 删除已消失的子弹
  for bullet in bullets.copy():
    if bullet.rect.bottom <= 0:
      bullets.remove(bullet)

  check_bullet_alien_collisions(ai_settings, screen, stats, sb, ship,
                                aliens, bullets)


def check_high_score(stats, sb):
  """Check to see if there's a new high score."""
  if stats.score > stats.high_score:
    stats.high_score = stats.score
    sb.prep_high_score()


def check_bullet_alien_collisions(ai_settings, screen, stats, sb, ship,
                                  aliens, bullets):
  # 响应子弹和外星人的碰撞
  # 删除发生碰撞的子弹和外星人
  collisions = pygame.sprite.groupcollide(bullets, aliens, True, True)

  if collisions:
    for aliens in collisions.values():
      stats.score += ai_settings.alien_points * len(aliens)
      sb.prep_score()
    check_high_score(stats, sb)

  if len(aliens) == 0:
    # 删除现有的子弹并创建一群外星人
    bullets.empty()
    ai_settings.increase_speed()

    # Increase level.
    stats.level += 1
    sb.prep_level()

    create_fleet(ai_settings, screen, ship, aliens)


def check_fleet_edges(ai_settings, aliens):
  # 有外星人到达边缘时采取相应的措施
  for alien in aliens.sprites():
    if alien.check_edges():
      change_fleet_direction(ai_settings, aliens)
      break


def change_fleet_direction(ai_settings, aliens):
  # 将整群外星人下移，并改变它们的方向
  for alien in aliens.sprites():
    alien.rect.y += ai_settings.fleet_drop_speed
  ai_settings.fleet_direction *= -1


def ship_hit(ai_settings, screen, stats, sb, ship, aliens, bullets):
  # 响应被外星人撞到的飞船
  if stats.ships_left > 0:
    # 将ships_left减1
    stats.ships_left -= 1

    # Update scoreboard.
    sb.prep_ships()

  else:
    stats.game_active = False
    pygame.mouse.set_visible(True)

  # 清空外星人列表和子弹列表
  aliens.empty()
  bullets.empty()

  # 创建一群新的外星人，并将飞船放到屏幕底端中央
  create_fleet(ai_settings, screen, ship, aliens)
  ship.center_ship()

  # 暂停
  sleep(0.5)


def check_aliens_bottom(ai_settings, screen, stats, sb, ship, aliens,
                        bullets):
  # 检查是否有外星人到达了屏幕底端
  screen_rect = screen.get_rect()
  for alien in aliens.sprites():
    if alien.rect.bottom >= screen_rect.bottom:
      # 像飞船被撞到一样进行处理
      ship_hit(ai_settings, screen, stats, sb, ship, aliens, bullets)
      break


def update_aliens(ai_settings, screen, stats, sb, ship, aliens, bullets):
  # 检查是否有外星人位于屏幕边缘，并更新整群外星人的位置
  check_fleet_edges(ai_settings, aliens)
  aliens.update()

  # 检查外星人和飞船之间的碰撞
  if pygame.sprite.spritecollideany(ship, aliens):
    ship_hit(ai_settings, screen, stats, sb, ship, aliens, bullets)

  # 检查是否有外星人到达屏幕底端
  check_aliens_bottom(ai_settings, screen, stats, sb, ship, aliens, bullets)


def get_number_aliens_x(ai_settings, alien_width):
  # 计算一行可容纳多少个外星人
  available_space_x = ai_settings.screen_width - 2 * alien_width
  number_aliens_x = int(available_space_x / (2 * alien_width))
  return number_aliens_x


def get_number_rows(ai_settings, ship_height, alien_height):
  # 计算屏幕可容纳多少行外星人
  available_space_y = (ai_settings.screen_height -
                       (3 * alien_height) - ship_height)
  number_rows = int(available_space_y / (2 * alien_height))
  return number_rows


def create_alien(ai_settings, screen, aliens, alien_number, row_number):
  # 创建一个外星人并将其加入当前行
  alien = Alien(ai_settings, screen)
  alien_width = alien.rect.width
  alien.x = alien_width + 2 * alien_width * alien_number
  alien.rect.x = alien.x
  alien.rect.y = alien.rect.height + 2 * alien.rect.height * row_number
  aliens.add(alien)


def create_fleet(ai_settings, screen, ship, aliens):
  # 创建一个外星人，并计算每行可容纳多少个外星人
  alien = Alien(ai_settings, screen)
  number_aliens_x = get_number_aliens_x(ai_settings, alien.rect.width)
  number_rows = get_number_rows(ai_settings, ship.rect.height,
                                alien.rect.height)

  # 创建外星人群
  for row_number in range(number_rows):
    for alien_number in range(number_aliens_x):
      create_alien(ai_settings, screen, aliens, alien_number,
                   row_number)
